A Brushless Dual-Mechanical-Port Dual-Electrical-Port Machine With Spoke Array Magnets in Flux Modulator

Brushless dual-mechanical-port dual-electrical-port (BLDD) permanent magnet (PM) machines have been gaining more and more attentions in recent years, with the merits of two decoupled rotors and contactless torque transmission. However, existing BLDD machines tend to suffer from low torque density due to low working flux density. In this paper, a BLDD machine with spoke array permanent magnets (PMs) in flux modular is proposed, which improves the torque density significantly. The structure and operation principle of the proposed machine are introduced. Detailed performance comparison between three different BLDD machine topologies, i.e., surface-mounted PM (SPM) BLDD machine, flux-bidirectional modulation (FBM) BLDD machine, and the proposed BLDD machine, is presented through finite element analysis (FEA). The analyzing results show that although the modulated magnetic field coupled with the modulation winding is slightly reduced, the torque transmission capability of the regular winding in the proposed BLDD machine is significantly enhanced when compared with that of its two counterparts. Index Terms-Brushless dual-mechanical-port dual-electrical-port (BLDD) machine, flux modulation effect, magnetic geared machine (MGM), spoke array permanent magne

Flexible Energy Conversion Control Strategy for Brushless Dual-Mechanical-Port Dual-Electrical-Port Machine in Hybrid Vehicles

Due to the advantages of high torque density and compact mechanical structure, brushless dual-mechanical-port dual-electrical-port (BLDD) PM machine has become a promising-alternative in series-parallel HEVs. However, two sets of windings in the same core may also result in flux cross coupling, which deteriorate control performance. Through special design of the magnetic circuit, the two sets of windings in the stator side are decoupled. In this paper, the mathematical model of BLDD-PM machine is analyzed firstly. Then, based on energy management system and the model of machine, the decoupled vector control algorithm for outer and inner rotor is developed. Next, common operation states under city road condition for hybrid vehicles have been summarized. According to operation state of HEV, the power flow analysis in the BLDD-PM machine system has been done. To validate the analysis results, experimental test under different operation condition has been conducted. Test results show good control performance of the BLDD-PM prototype and verify the correctness of analysis. Index Terms-BLDD-PM machine, power flow analysis, HEV

Fault-Tolerant Capability and Torque-Speed Measurements of Permanent Magnet Brushless AC Machines

In this paper, the fault-tolerant capability in terms of inductance profile of a dual-stator permanent magnet brushless AC machine is presented. Similarly, its power-speed and torque-speed characteristics are also predicted. Special reference is made to the impact of different rotor pole numbers. A 2D-finite element analysis (FEA) procedure is adopted in this work, and the cross-coupling effect of the machine inductances owing to the influence of direct-axis and quadrature-axis currents is also taken into consideration. The results show that, the investigated machine having odd number of rotor poles would exhibit better fault-tolerant capability compared to their counterparts with even number of rotor poles. Further, the machine having 6-stator slots and 13-rotor poles i.e. 6Slots-13P machine has the greatest field-weakening potential owing to its high full-speed to rated speed relation. The studies also show that, the investigated machines have negligible reluctance torque due to their basically unity saliency ratios obtained from the machines’ almost similar quadrature-axis inductance, Lq, and direct-axis inductance, Ld, values.Keywords: Direct-axis, Quadrature-axis, Inductance, Power, Speed, Torque, AC machines, Permanent magnet

Milestones, hotspots and trends in the development of electric machines

As one of the greatest inventions of human beings, the electric machine (EM) has realized the mutual conversion between electrical energy and mechanical energy, which has essentially led humanity into the age of electrification and greatly promoted the progress and development of human society. This paper will briefly review the development of EMs in the past two centuries, highlighting the historical milestones and investigating the driving force behind it. With the innovation of theory, the progress of materials and the breakthrough of computer science and power electronic devices, the mainstream EM types has been continuously changing since its appearance. This paper will not only summarize the basic operation principle and performance characteristics of traditional EMs, but also that of the emerging types of EMs. Meanwhile, control and drive system, as a non-negligible part of EM system, will be complementarily introduced. Finally, due to the background of global emission reduction, industrial intelligentization and transportation electrification, EM industry will usher again in a golden period of development. Accordingly, several foreseeable future developing trends will be analyzed and summarized

Investigation of Novel Axial Flux Magnetically Geared Machine

As axial flux permanent magnet (AFPM) machines are currently the most appropriate topologies for limited axial space applications, a novel axial flux magnetically geared permanent magnet (AFMGPM) machine is investigated in this thesis. Based on a yokeless and segmented YASA machine, a new AFMGPM topology was designed and studied. The proposed AFMGPM machine consists of stator segments equipped with concentrated windings and two PM rotors with different pole-pair numbers: a high speed rotor (HSR) and low speed rotor (LSR). The proposed AFMGPM offers the merit of simple mechanical structure and is suitable for applications with limited axial space. Two possible rotor pole combinations were selected and designed with the same stator segments: MG12/5-7 with HSR pole pairs of 5 and LSR pole pairs of 7, and MG12/4-8 with HSR pole pairs of 4 and LSR pole pairs of 8. These were optimised for maximum torque capability. Performance comparisons at no-load and on-load conditions using 3D-finite element analysis (FEM) reveal that the machine torque performance is sensitive to the PM dimensions and better performance can be obtained with the MG12/5-7 topology. It is demonstrated that the MG machines are a valid alternative to the conventional planetary gear function in HEVs. Combining the conventional PM machine with the MG machine has made it possible to replace the power split components using only one electrical device. Additionally, the proposed machine can work as a conventional magnetic gear (MG) and a generator. It is shown that the new AFMGPM machine can realise the function of power split devices in conventional HEVs, as a mechanical planetary gear, motor and generator. It is further shown that the rotor manufacturing tolerance has a significant effect in terms of stator/LSR misalignment on the no-load and on-load performances of the machine. Finally, a performance comparison between the novel machine and the conventional axial flux YASA machine is performed. To validate the predicted results of finite element analysis, a prototype of the new topology and a conventional YASA machine are manufactured and tested. It has, showing that with the benefit of two rotors with different torques and speeds, the new AFMGPM machine has superior performance at all load conditions

Magnetic Gears and Magnetically Geared Electrical Machines with Reduced Rare-Earth Materials

This thesis covers a new emerging class of electrical machines, namely, Magnetic Gears (MGs) and Magnetically Geared Machines (MGMs). This particular kind of gears/machines are able of either scaling up or down the revolution-per-minute to meet various load profiles as in the case of mechanical gearboxes. Mechanical gearboxes have historically dominated various applications due to their relatively high torque density. However, mechanical gearboxes require physical contact between the rotational components, whereas MGs and MGMs accomplish fundamentally the same function via a contactless mechanism. This physical isolation between the rotational components lead to several advantages in a favor of MGs and MGMs over mechanical gearboxes. Although MGs and MGMs can potentially provide a solution for some of the practical issues of mechanical gears, MGs and MGMs have two major challenges that researchers have been trying to address. Those challenges are the high usage of rare-earth Permeant Magnet (PM) materials and the relatively complex mechanical structure of MGs and MGMs both of which are a consequence of the multi-airgap design. As in any engineering field, materials play a significant role and present a trad-off between the performance and cost. In addition to the previous trad-off, the concern with rare-earth PM materials is sustainability as well as price fluctuations. Current research in electrical machines demonstrate real initiatives to reduce the cost of electrical machines by reducing/eliminating the PM rare-earth content while attempting to maintain a competitive electromagnetic performance. Most advanced electrical machines use Dy-NdFeB PM with high energy product at elevated temperatures. Dysprosium (Dy) is one of heavy rare-earth elements and the key source of the price volatility. As a consequence, this thesis aims to address foregoing PM material challenges and investigate the electromagnetic performance of designs that blend different PM types in the context of MGs and MGMs. In addition, practical designs will be proposed in order to reduce the complexity related to the nature of MGs and MGMs

Power quality improvement utilizing photovoltaic generation connected to a weak grid

Microgrid research and development in the past decades have been one of the most popular topics. Similarly, the photovoltaic generation has been surging among renewable generation in the past few years, thanks to the availability, affordability, technology maturity of the PV panels and the PV inverter in the general market. Unfortunately, quite often, the PV installations are connected to weak grids and may have been considered as the culprit of poor power quality affecting other loads in particular sensitive loads connected to the same point of common coupling (PCC). This paper is intended to demystify the renewable generation, and turns the negative perception into positive revelation of the superiority of PV generation to the power quality improvement in a microgrid system. The main objective of this work is to develop a control method for the PV inverter so that the power quality at the PCC will be improved under various disturbances. The method is to control the reactive current based on utilizing the grid current to counteract the negative impact of the disturbances. The proposed control method is verified in PSIM platform. Promising results have been obtaine

Advances in Rotating Electric Machines

It is difficult to imagine a modern society without rotating electric machines. Their use has been increasing not only in the traditional fields of application but also in more contemporary fields, including renewable energy conversion systems, electric aircraft, aerospace, electric vehicles, unmanned propulsion systems, robotics, etc. This has contributed to advances in the materials, design methodologies, modeling tools, and manufacturing processes of current electric machines, which are characterized by high compactness, low weight, high power density, high torque density, and high reliability. On the other hand, the growing use of electric machines and drives in more critical applications has pushed forward the research in the area of condition monitoring and fault tolerance, leading to the development of more reliable diagnostic techniques and more fault-tolerant machines. This book presents and disseminates the most recent advances related to the theory, design, modeling, application, control, and condition monitoring of all types of rotating electric machines